Portable heater



FIG. 1 is a perspective view of the portable heater design;

FIG. 2 is a left side view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a front view thereof.

The broken lines are for illustrative purposes and form no part of the claimed design and to define boundaries between claimed and unclaimed portions of the claimed design. 

The ornamental design for a portable heater, as shown and described. 